Radar antenna lobing power-divider



20,1957 F. A. MARASCO ETAL 2,303,317

RADAR ANTENNA LO BING POWER-DIVIDER Filed Aug. 18, 1952 2 SheetsSheet l 3| 35 T2 BOX SYNCHRONIZING 33 SELSYN SYSTEM 3s -21 34 ANTENNA 3%?63313? l 22(C'Ho|u: JOINT) RADAR TRANSMITTER AND azcanvzsz.

FIGURE I. INVENTOR.

FRANCIS A. MARASCO EDWIN S. OXNER 1957 F. A, MARASCO EIAL 2,803,817

RADAR ANTENNA LOBING POWER-DIVIDER Filed Aug. 18, 1952 2 Sheets-Sheet 2 F IGURE 2. INVENTOR.

I FRANCIS A. MARASCO BY EDYLIN S.OXNER atent Ofilice 2,803,817 Patented Aug. 20, 1957 2,803,317 RADAR ANTENNA LoBrNG POWER-DIVIDER Francis A. Marasco and Edwin S. Oxner, Indianapolis,

Ind, assignors to the United States of America as represented by the Secretary of the Navy The invention described herein may be manufactured and used by or for the Government of the United States of America for'governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates generally to radar tracking antennas, and more particularly to a lobing, powerdividing waveguide therefor, adapted to simultaneously transmit, and sequentially receive, pulses.

Prior art devices of this type achieved lobing by either a mechanical switching between two antennas or, when only a single antenna is used, by shifting the phase of one-half of the antenna with respect to the other to produce a double lobed pattern of radiation. This phasing may be accomplished electromechanically or electronically. The mechanical switching system is simple in operation and trouble free, but it is ineflicient in the use of equipment and space since it requires two antennas. The electromechanical phasing system is more efiicient than the mechanical system in itsutilization of equipment and space, but is subject to the disadvantages that any instaoility introduced into the phasing mechanism by mechanical imperfection would appear as distortions in the received image. The electronically switched phasing system has the disadvantage of introducing additional complex electrical circuits into an already complex mechanism thereby increasing the possibility of fault and the difiiculty of maintenance. All of these prior art lobing systems have the limitation that the lobe switching occurs both on the transmission and receiving cycle.

It is therefore the principal object of this invention to provide a lobe switching system which permits the transmission of a single lobe while switching the lobes for reception.

A second object of the invention is to mechanical means to switch the lobes.

A third object is to provide for neutralizing the lobe switching while transmitting, thereby permitting no reflection of transmitted power to occur.

A fourth object of this invention is to provide a waveguide powendivider in which maximum attenuation is possible in one of two divisions when the other division is conducting.

A fifth object of the invention is to provide a waveguide power-divider structure which produces negligible reflected waves in the system.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. 1 is a schematic diagram of the device.

Fig. 2 is the perspective view of the power-divider.

Referring now to the drawing where like reference characters designate like or corresponding parts throughout the several views, there is shown in Fig. 1 a diagrammatic representation of a conventional radar system adapted to incorporate the present invention, in which numerals 11 and 12 designate two electromagnetic feed horns of the provide simplified section and the fired 2 antenna 13 with reflector 14. The horns 11 and 12 are connected to the power-divider of the present invention which is generally designated as 16 and includes a section of rectangular wave-guide 17 designed to operate in the standard TE1,0 mode or TE'n,o' mode, in which TE refers to the transverse electric field and the first subscript refers to the number of /2 wave-length patterns along the long side of the wave-guide, and the second subscript refers to the number of /2 wave-length patterns along the short side of the wave-guide, n being any whole number, and said section 17 having a conducting partition 18 which equally divides the section of the wave-guide in the axial direction and which is perpendicular to the direction of the transverse electrical field, as can be more clearly seen in Fig. 2, thereby forming two wave-guide channels 19 and 21. Since this partition divides the narrow side of the wave-guide it does not afiect the wave-length response of the guide, but the electrical field strength will be divided according to the relation E h V' b where V1 is the field strength across the divided section having an end width of 121, and V2 is field strength across the other section which has a width of b2 where V1+V2= the total field strength before division and b1+b2=the total width of the wave-guide in the direction perpendicular to the transverse magnetic field. The power-divider 16 is connected at one end by means of a choke or cover joint 22 of standard construction to a feed line wave-guide 23 which connects to the transmitting and receiving circuits indicated by box diagram at 24. The other end of the divider 16 is connected to the antenna feed wave-guides 25 and 26, which are of standard size, by an impedance matching section 27 connected to each of the channels 19 and 21 of the power-divider. It has been found desirable to bevel the end of partition 18 at 28 to prevent reflection of the waves entering the powerdivider from the transmitter with the attendant establishment of standing waves and the consequent loss in radiated power. switching or lobing device, there are provided two series stub sections 29 and 31, one in each of the channels 19 and 21. These stub sections 29 and 31 are attached to TR boxes 32 and 33 containing the usual TR tubes and when so connected are proportioned in length to produce the equivalent of a /2 wave-length shortened stub when the TR tube is fired. It is found that by placing these stub sections in the channels of the divider rather than in the full size wave-guide a much higher degree of attenuation is obtained. The stub sections 29 and 31 are extended beyond the TR box such a distance as to produce a section length of an odd number of wave-length. The outer ends of the stubs are alternately closed with semicircular rotatable shorting closure plates 34 and 35 which are mounted in opposed and spaced relation on a shaft 36 which is driven by motor 37. Said shaft is also connected to a synchronizing selsyn system 38. Here it has been found desirable to use a choke collar to allow for elficient operation of the closures. The provision of the choke joint permits the semi-circular closing plates to be spaced from the end of the stub section with sufficient clearance for good mechanical operation without appreciable loss in electrical efliciency. There is also provided the usual tracking mechanism, indicated at 39, to position the antenna.

In operation the transmitted impulses from the transmitter enters the power-divider and when it reaches each of the stub sections sufiicient power enters the stub to fire the TR tubes producing the equivalent of a short circuit across the entrance to the stub section, since the stub TR box are equivalent to a /2 To adapt the power-divider for use as a lobewhich, givestav high impedance in the channels.

J V wave-length section, thereby permitting both channels of the. power-divider to. simultaneously transmit the. impulse from the transmitter to the antenna.

When the transmitting pulse is complete the TR tubes c ase firing and-the. stub'sectio'n becomes'an open circuit 870; long" as the end of the stub section is open, but as the semi-circular plates', 34 and 35 are rotated they successively close-and-open thelstub'sections to produce alternately a shortof the stub se'ctiomwhich gives a low impedance in channels of the power-divider, and an open stub section, When thefstub section. is shorted by the closing of the open end by the plate that channel of the divider will conduct while the otherstub sec'tionremains open and the high impedance reflected. into the "corresponding division of the divide: produces a high degree of attenuation while the alternate. reception of the reflected signal through the two feed horns produces a lobing effect.

Thepower-divider described above in connection with radar 'lobing could obviously be used wherever it was desirable. to, provide. for alternate reception or through two channels, injwhich case the closing of ends of the stub sections could be accomplished by hand or other suitable mechanical means.

It should be understood; of course, that the foregoing disclosure relates to only a preferred embodiment of the invention and that numerous modifications or alterations may be made therein without departing from the spirit and the scope of the invention.

What is claimed and desired to be protected by Letters Patent of the United States is:

' 1. In combination with a radar transmitting and receiving system, a power-divider comprising a section of wave-guideof suitable dimension to operate at the desired-frequency in the desired mode having longitudinal conducting partition forming two channels of reduced cross-sectional area, two transmit-receiver boxes, means connectingone of said boxes in series with each of said channels,-said means comprising a first pair of stub sections which when connected between each of said boxes and its corresponding channel produces a wave-guide section an equivalent half wavelength long, a second pair of stub sections of a Wave-guide, one of said second pair connected at one of its ends to each of said transmitreceive boxes to produce with the first stub, section and the transmit-receive box a wave-guide section'an equivalent odd quarter wavelength long, means for alternately shunting said second pair of stub sections.

2. In a radar system a power-divider for use with a rectangular Wave-guide, said divider being connected between a transmitter-receiver and an antenna, said divider comprising two tubular channelsof rectangular cross-section connected in a Y connection to the wave-guide from the transmitter-receiver, each of said tubular channels havingone of its cross-sectional dimensions smaller than the corresponding cross-sectional dimension of the waveguide to which it is connected, a first means for simultaneously rendering the two tubular channels conductive, a second means operative to render said channels alternately conducting when said first means is inoperative, said first means consisting of a TR tube in a TR box connected at right angles to each of the channels by a stub section of arlength toproduce in series with the TR box the equivalent of a /2 wave-length shorted stub when the TR tube'fires, said second means including a stub section extending beyond each of the TR boxes a distance to provide.

in series with the TR boxes stub sections of an off muliple of /4 wave-lengths when open and being provided with means for sequentially closing and opening the open ends of said stub sections.

3. A device as claimed in claim 2 in which the means for sequentiallyjclosing and opening the open ends of thestubsections comprises a rotatable shaft having semicircular plates mounted in opposed and spaced relation to each other and being mounted adjacent the stub sec-. tions so that the semi-circular plates will alternately close and open the open end of the stub sections when the shaft is revolved; a motor connected for rotating said shaft.

I References Cited in the file of this patent UNITED STATES PATENTS 2,189,549 Hershberger Feb. 6, 1940 2,396,044 Fox Mar. 5, 1946 2,509,196 Corke et al. May 23, 1950 2,577,158 Rosencrans Dec. 4, 1951 2,585,855 Sherwin et al. Feb. 12, 1952 2,597,607 Alford et al. May 20, 1952 2,618,777 Ashmead Nov. 18, 1952 2,627,020 Parnell et al. Jan. 27, 1953 

